Falling film plasma reactor

ABSTRACT

A falling film plasma reactor (FFPR) provides a number of benefits for the treatment of process gases. The falling film plasma reactor uses high voltage alternating current or pulsed direct current which is applied to radially separated electrodes to thereby create a dielectric breakdown of the process gas that is flowing within the large radial gap between the two electrodes. Typical plasma reactors often utilize fixed dielectric construction which can result in potential failure of the device by arcing between the electrodes as portions of the dielectric fail. Such failures are prevented by using a dielectric liquid that constantly flows over the electrodes, or over a fixed dielectric barrier over the electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional application Ser.No. 60/162,918 filed on Nov. 1, 1999, incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains generally to chemical treatment systems, andmore particularly to a modular point of use chemical treatment systemthat permits individual treatment of specific chemical process mixtures.

2. Description of the Background Art

Several point-of-use chemical treatment systems are commerciallyavailable which utilize thermal, wet scrubbing, dry scrubbing,catalytic, or plasma technologies. However, the current implementationsof these technologies tend to suffer from poor economic feasibility orlow chemical treatment efficiency due to the need for multiple andsimultaneous treatment of specific chemical process mixtures. Manyequipment manufacturers accommodate the need for process specifictreatment solutions by offering several different products, based upondifferent technology implementations, that provide solutions forindividual specific process mixtures and not for multiple processmixtures. Because of the vast number of different process streams thatmay need to be treated, a commensurate number of standalone abatementtechnologies and systems have been developed, most notably those thatare described in the following discussion.

Thermal reactors utilize a variety of means to heat chemical processmixtures to high equilibrium temperatures. In addition, reagent gasesare added to promote specific reaction chemistries; for example, oxygenor air can be added to promote oxidation. The chemical process mixturecan be heated upon contact with a hot surface or through mixing with hotgas. However, hot surface reactors are greatly susceptible to corrosionfailure and material accumulation leading to clogging. Common hot gasreactors utilize combustion to heat and react the chemical processmixture in the gas phase. Combustion systems are extremely sensitive tofuel gas and oxidizing gas control and mixing. Corrosion and materialaccumulation on injection nozzles and igniters result in degradedperformance of these systems unless frequent maintenance is performed. Asignificant expense and liability associated with combustion systems isthe piping of fuel gas (specific to the combustion reactor) throughoutthe manufacturing facility to permit equipment installation.

Glow discharge plasmas are capable of depositing much of their appliedpower into the gaseous medium to achieve a high percentage of ionizationor dielectric breakdown. Such devices operating with electrodepotentials of several hundred volts can deposit several kilowatts ofpower using high frequency alternating current. Consequently, plasmaprocesses creating energetic electrons, ions, reactive neutrals, andradical species can be promoted in these devices. Complex and diverseplasma chemistries can be conducted, but only at low relative pressures,typically 1 millitorr to 10 torr. Coupling power into the gas streambecomes difficult above these pressures resulting in non-uniformdielectric breakdown and collapse of the plasma region to the electrode(inductively coupled) or electrodes (capacitively coupled) of thesedevices. Because low pressure operation requires pumping systems, thechemical throughput is directly dependent upon both the scale of thepumping system and the ability to apply high frequency power. Inaddition, changes to the electrode material or geometry occur as aresult of corrosion and material accumulation. Such changes interferewith power coupling to the plasma as a result of detuning and energydissipation by deposited materials. Chemical processing applicationshave been limited to low flow gas processing such as chemical vapordeposition, gas phase chemical etching, gas phase spectroscopy, orsurface treatment of materials such as fibers and films.

Microwave plasmas are also limited to low pressure operation. Aspressures approach 100 torr, the inability to propagate and tunecoherent waves limits the ability to deposit energy within a resonantcavity resulting in plasma collapse to the cavity surface. As lowpressure operation requires a pumping system, the chemical throughput isagain directly dependent upon both the scale of the pumping system andthe ability to couple high frequency power. In addition, changes to thecavity material or geometry occur as a result of corrosion and materialaccumulation. Such changes interfere with power coupling to the plasmaby changing the modes of TE and TM fields propagated within the cavity.

Silent discharge plasmas are capable of operating at relatively high gaspressures, typically above one atmosphere. Dielectric breakdown of gasesbetween electrodes with a relatively large separation can be achievedusing high voltage potentials. However, such devices require adielectric barrier between the electrodes and the gas stream to preventcollapse of the plasma due to arcing. The electrical resistance of thedielectric barrier enhances capacitive coupling of power to the plasma,but this resistance also limits the current flow through these devices.While silent discharge plasmas are capable of promoting complexchemistries, plasma chemical activity diminishes dramatically as afunction of increased gas flow. Minimizing the dielectric strength ofthe electrode barrier by placing dielectric material throughout thedischarge gap has provided enhanced power deposition, but thecomplexities of surface reaction chemistries as well as physical foulingare increased. Thus, catastrophic arcing remains the principal failuremode and limiting factor in power deposition within these plasmadevices.

Catalytic reactors require moderately high temperatures to promotechemical reactions and desorb reaction products from the catalystsurface. The process gas is preheated by either hot surface contact orgas phase combustion. Therefore, maintenance considerations for thepreheating section of the system are similar to those for thermalreactors. Additionally, reaction products can poison the catalystsurface by forming a physical barrier or by chemically bonding to thesurface. Where reaction products remain as solids even at hightemperatures, physical poisoning occurs. Additionally, locations wherereaction products are highly oxidizing or capable of forming stablesalts upon reaction with the catalyst, chemical poisoning occurs.

Wet scrubbers require relatively meager amounts of energy for operationsince their functionality extends from the inherent chemical affinitybetween the scrubbing solution and the process gases being treated. Bothchemical reactivity and solubility are principle parameters effectingthe efficiency and capacity of the scrubbing process. Mass transfer isthe physical parameter most important to the efficiency of the scrubbingprocess. Two primary distinctions are important to properly applying wetscrubbing technology: (1) simple liquid with or without additionalreagents, and (2) low energy or high energy. The first distinctiondictates the ability to satisfy the chemical parameters for scrubbingwhen treating specific gases. The second distinction dictates theability to ensure the requisite physical contact between gaseous orparticulate matter and the scrubbing liquid to effect removal. Treatmentrequirements that create difficulties for wet scrubbers are hazardousprocess mixtures comprising both gaseous and particulate matter wheresome of the gases are largely insoluble in the scrubbing liquid suchthat insufficient reaction occurs with the specific reagents, andparticulate having diameters in the nanometer to submicron range isthereby formed prior to, or during, the scrubbing process.

Dry scrubbers vary greatly with regard to energy requirements whichrange from a simple fixed bed adsorption system having low powerconsumption levels, to a heated reagent bed having a power consumptionwhich approaches that of a catalytic system. Pressure swing ortemperature swing adsorption systems have not been feasible for treatingcomplex and reactive gas mixtures and are, therefore, not discussed.Primary distinctions between various dry scrubbers are physicaladsorption, and chemical adsorption. Physical adsorption refers tocondensation or molecular trapping processes which occur within therequisite material matrix. Chemical adsorption refers to a combinationof physical adsorption and surface chemical reaction processes whichbind the molecules of concern to the requisite material matrix. Oftenchemical adsorption systems require added thermal energy to promote thenecessary surface reactions. In both types of dry scrubbers the commonconcerns are premature clogging of the material matrix by particulateformed upstream, and a limited capacity which requires regularreplacement and disposal of the material matrix.

As can be seen, therefore, a number of abatement options are availablefor the process streams in semiconductor wafer manufacturing. However,the equipment available is generally constructed such that its abatementcapabilities are limited to one or two process streams. Industryeconomics (both cost and space availability) largely dictate that atypical treatment system must simultaneously treat at least four processstreams to be feasible. Typical semiconductor wafer manufacturingequipment can simultaneously carry out multiple chemical processingoperations. Thus, a single treatment system that is optimized for one ortwo chemical processes suffers the loss of chemical treatment efficiencyand severe maintenance requirements from exposure to the additionalchemical process mixtures. Furthermore, because many of the materialsrequiring treatment are pyrophoric or flammable, serious risk ofexplosion and fire is associated with poor treatment efficiencies orequipment bypass during unplanned maintenance. Currently, thesemiconductor wafer manufacturer is forced to make a compromise inselecting treatment equipment and accept the inherent risk, thuscreating a need for a system that is economic, reconfigurable andreliable. The present invention satisfies that need, as well as others,and overcomes deficiencies in current treatment systems.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises a modular point-of-use chemicaltreatment system employing interchangeable inlet modules which interfaceto a modular base unit that preferably contains a primary scrubber. Inorder to optimize individual treatment of specific chemical mixtures andprocess streams, the inlet modules may be used in combinations, such asby combining high energy reactors, plasma reactors, and scrubbers. Themodular system is provided with integrated controls and safetyinterlocks to permit several different simultaneous unit operations.Reconfiguration of the treatment system, including system expansion, isfacilitated through the use of a completely modular subsystem andpreferably even the equipment cabinet itself. The modular design of thepresent invention eliminates the necessity of using an abatementapparatus that is limited to treatment of a particular type of chemicalcomposition or specific process stream.

In accordance with an aspect of the invention, a porous wall thermalreactor which utilizes a thermal process for pyrolizing and oxidizinghazardous materials is provided. A preheated reagent gas is introducedinto the thermal reactor through a preferably porous cylindrical reactorwall. Staged mixing of the process gas flowing through the reactor withhot reagent gas causes gas phase reaction of these chemical species,thereby creating new chemical constituents, including gas andparticulate matter which are shielded from the reactor wall by theintruding hot reagent gas. These chemical constituents are swept throughthe reactor and mixed with a cooling gas prior to entering thesubsequent scrubbing unit.

In accordance with another aspect of the invention, a falling filmplasma reactor which utilizes a high voltage alternating current, orpulsed direct current, is provided. Falling film reactors are typicallyutilized for reducing metallic oxides, such as Fe₂O₃, and Fe₃O₄. Theelectrical current is applied to radially spaced cylindrical electrodesfor creating a dielectric breakdown of the process gas flowing within alarge radial gap between the two electrodes. Arcing between theelectrodes is prevented by passing a dielectric liquid over theelectrodes, or a fixed dielectric barrier over which a conductive ordielectric liquid is caused to flow. A reagent gas introduced into theprocess gas causes electrical energy deposited into the plasma todissociate atoms and molecules of the gas stream constituents.Subsequent reaction of these chemical species creates new chemicalconstituents, including gas and particulate matter which contacts theliquid flowing over the electrodes and is absorbed, or reacted, with theliquid and its constituents. The treated process stream is therein sweptthrough the reactor and mixed with a cooling gas prior to entering thesubsequent scrubbing unit.

In accordance with another aspect of the invention, universal coolingair sleeves interface the high energy reactors, or basic scrubber inlet,to a liquid spray chamber containing an integral liquid recirculationpump and drain/sump. The liquid spray chamber includes an outlet flangedto accommodate two distinct types of modular scrubbing units. The firsttype of scrubbing unit comprises an extended height, high efficiencycounter-current, packed bed liquid scrubbing tower which interfaces withthe liquid recirculation to provide long residence times and highliquid-to-gas ratios. The second type of scrubbing unit comprises bothan abbreviated height, moderate efficiency counter-current, packed bedliquid scrubbing tower which interfaces with liquid recirculation, and afixed bed dry scrubber with in-situ regeneration capability.

In accordance with yet another aspect of the invention, a basic scrubberinlet that eliminates back mixing of downstream gases is provided. Inparticular, back mixing is reduced for gases which are introduced intothe scrubbing unit from separate process inlets that provide stagedmixing of the process gas mixture flowing through the inlet nozzle. Thefirst stage can preferably utilize an inert gas sheath which isolatesthe inlet nozzle from the gas by increasing the inlet throat diameter toreduce gas velocity. The second stage preferably utilizes a high flowair sheath which isolates the exhaust nozzle from the scrubbing liquiddroplets and vapor, such that the resultant process gas mixture,additional nitrogen, and clean dry air, are swept into the subsequentscrubbing unit.

In accordance with still another aspect of the invention,interchangeable particulate collectors are incorporated into the exhauststream of the scrubbing tower to separate liquid and solid particulatesfrom the exhaust gas stream. Two alternative collector embodiments arepreferred for separating the particulates from the exhaust gas. Anembodiment of the present invention utilizes a collector comprising aseries of impactor plates designed to efficiently remove particlediameters ranging from submicron to low micron. The surfaces of theplates are continuously washed with scrubbing liquid to facilitateparticle collection. The second embodiment comprises an air poweredejector which accelerates particles at right angles to a collectionsurface to thereby effect a removal of particles with diameters in themicron range. The air powered ejector simultaneously enhances theexhaust draw on the modular abatement system and depresses the exhaustgas dew point to minimize downstream vapor condensation.

An object of the invention is to provide a chemical abatement systemcapable of deployment at the point of use.

Another object of the invention is to provide a modular chemicalabatement system that supports several treatment regimens.

Another object of the invention is to optimize individual treatment ofspecific chemical mixtures.

Another object of the invention is to allow for simultaneous operationof several different treatment units.

Another object of the invention is to provide a system that can berapidly reconfigured, by the replacement of modules, for a variety ofprocess streams.

Another object of the invention is to provide a system with integratedcontrols and safety interlocks, whereupon changing the type of modulartreatment units, the controls may be set for the proper parameters forthe new module, such as flow rate, temperature, and pressure, tooptimize system performance.

Another object of the invention is to allow for the coupling of highenergy reactors with chemical scrubbing units configured for specificchemical mixtures.

Another object of the invention is to provide an abatement system havinga thermal reactor which is capable of pyrolizing and oxidizing hazardousmaterials.

Another object of the invention is to provide an abatement systemutilizing a porous wall thermal reactor in which the buildup ofparticulate is minimized.

Another object of the invention is to provide an abatement system havinga thermal reactor having a porous wall configured for easy cleaning.

Another object of the invention is to provide an abatement system havingmultistage particulate collectors comprising impactor plate designs andair powered ejectors such that a range of particulate sizes are removed.

Another advantage of the invention is to provide for the recovery ofuseful chemical compositions and elements, such as Gallium, from thescrubber fluid.

Further objects and advantages of the invention will be brought out inthe following portions of the specification, wherein the detaileddescription is for the purpose of fully disclosing preferred embodimentsof the invention without placing limitations thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood by reference to thefollowing drawings which are for illustrative purposes only:

FIG. 1 is a schematic diagram of a modular point-of-use chemicaltreatment system according to an embodiment of the present invention,shown with interchangeable treatment units.

FIG. 2 is a schematic diagram of porous thermal wall reactor operationaccording to an aspect of the present invention.

FIG. 3A is a side schematic view of a thermal reactor according to anaspect of the present invention, which is shown prior to disassembly.

FIG. 3B is a side schematic view of the thermal reactor shown in FIG. 3Ain which the core has been removed to allow for replacement ormaintenance.

FIG. 4 is a schematic diagram of a falling film plasma reactor accordingto an aspect of the present invention shown with an inner electrodeassembly, outer electrode assembly, and a reactor housing.

FIG. 5 is a side schematic view of the modular chemical abatement systemaccording to an embodiment of the present invention showing a cutaway ofthe primary and secondary scrubber units.

FIG. 6 is a side schematic view of a particulate collector according toan aspect of the present invention showing a series of removableimpactor plates.

FIG. 7 is a top view of an impactor plate as shown in FIG. 6 forattachment within the particulate collector.

FIG. 8 is a side schematic view of an air powered ejector according toan aspect of the present invention.

FIG. 9 is a partial side schematic view of a modular abatement systemaccording to the present invention shown configured with four thermalreactors, two of which are shown, along with an associated universal aircooling sleeve, prior to installation.

FIG. 10 is an left end schematic view of the modular abatement system ofFIG. 9 which shows the pneumatic and hydraulic connection of a thermalreactor.

FIG. 11 is a side schematic view of an alternative embodiment of themodular abatement system of FIG. 9 in which the secondary scrubber hasbeen replaced with a two phase scrubber utilizing a dry scrubber firststage and a wet scrubber second stage.

FIG. 12 is a perspective partial exploded view of a scrubber inletassembly according to an aspect of the present invention.

FIG. 13 is a perspective partial exploded view of a housing for use withthe scrubber inlet assembly of FIG. 12.

FIG. 14 is a side view of a modular porous wall thermal reactoraccording to an aspect of the present invention.

FIG. 15 is a perspective view of a sleeve nozzle for use within theporous wall thermal reactor shown in FIG. 14, showing the inlet areasfor source gas and inert gas.

FIG. 16 is a partial cross-section view of the thermal reactor showingan insulating wall through which the heated gas is delivered to a porouscylindrical core.

FIG. 17 is a perspective view of a porous wall cylindrical core for usewithin the thermal reactor shown in FIG. 16 according to an aspect ofthe present invention.

FIG. 18 is a perspective view of a porous wall conical core for usewithin thermal reactors according to another embodiment of the presentinvention.

FIG. 19 is a top plan view of the thermal reactor housing without thereactor core, which shows the tangential heater input.

FIG. 20 is a perspective view of a ceramic conduit for use within thethermal reactor of FIG. 16.

FIG. 21A is a side view in cross-section of a thermal reactor accordingto an embodiment of the present invention shown assembled with the coreassembly.

FIG. 21B is a cross-sectional view of the thermal reactor of FIG. 21Ashown with the core assembly removed from the reactor housing.

FIG. 22 is a side view of the sleeve nozzle of FIG. 15 shown configuredwith a slidably engaged porous thermal core cleaning device.

FIG. 23 is a side view in partial cross-section of a universal coolingair sleeve according to an aspect of the present invention.

FIG. 24 is a top view of the universal cooling air sleeve of FIG. 23,showing the air inlet tube.

FIG. 25 is a schematic diagram showing the operation of a falling filmplasma reactor according to an aspect of the present invention.

FIG. 26 is a side view of an inner electrode assembly for a falling filmplasma reactor according to an aspect of the present invention.

FIG. 27 is a side view of an outer electrode assembly for a falling filmplasma reactor whose inner electrode is shown in FIG. 26.

FIG. 28 is a perspective exploded view of a protective housing tosurround the falling plasma reactor whose outer electrode is shown inFIG. 27.

FIG. 29 is a perspective exploded view of a liquid/gas phase separatorshown with a reactor mounting plate which may be connected to thefalling film plasma reactor according to an aspect of the presentinvention.

FIG. 30 is a block diagram of the system hydraulic flow according to anembodiment of the present invention.

FIG. 31 is a block diagram of the system pneumatic flow according to anembodiment of the present invention.

FIG. 32 is a block diagram of system electronics according to anembodiment of the present invention shown interconnected for controllingand monitoring the system.

DETAILED DESCRIPTION OF THE INVENTION

Referring more specifically to the drawings, for illustrative purposesthe present invention is embodied in the apparatus generally shown inFIG. 1 through FIG. 32. It will be appreciated that the apparatus mayvary as to configuration and as to details of the parts, and that themethod may vary as to the specific steps and sequence, without departingfrom the basic concepts as disclosed herein.

In general terms, the invention comprises a modular point-of-usechemical treatment system utilizing interchangeable inlet modulesinterfaced to a modular base unit, such as a primary scrubber, andpreferably capable of supporting additional chemical scrubbing modules.System components are designed and packaged to minimize the time andeffort required for installation and maintenance while maximizinglifetime and performance. Integrated controls and safety interlockspermit simultaneous operation of several different unit operations.Rapid reconfiguration of the treatment system, including expansion, isfacilitated through the use of fully modular subsystems. The inventioncan be utilized with various reactor configurations, including theporous wall thermal reactor and falling film plasma reactor describedherein.

A process stream from a manufacturing process first enters the modularabatement system, hereafter often referred to simply as the “system”, byway of a system inlet module. A variety of system inlet modules may beconfigured for use within the system for the selective treatment ofprocess streams. The present invention teaches the use of three types ofinlet modules: (1) thermal reactors, exemplified as a porous wallthermal reactor (PWTR); (2) plasma reactors, exemplified as a fallingfilm plasma reactor (FFPR); and (3) scrubber inlets, exemplified as atwo stage scrubber inlet (TSSI). By way of example, and not oflimitation, selective treatment may comprise the use of a porous wallthermal reactor, which might be preferred for treating an aluminum etchprocess with particulate-forming and chloride compounds; while thefalling film plasma reactor might be preferred to treat a siliconnitride etch process with particulate-forming and fluoride compounds.The need to utilize wet chemical scrubbing dictates the selection of thescrubber inlet. For example, a two stage scrubber inlet might bepreferred for an epitaxial silicon etch process with high flows ofhydrogen chloride.

FIG. 1 shows a two inlet modular abatement system 10 according to theinvention having a modular base unit 12, that preferably has acylindrical cross-section, containing a reservoir of liquid 14. Ingeneral application, the modular base 12 is configured as a primaryscrubber, and may alternatively be referred to as primary scrubber 12.An upper portion of the primary scrubber 12 is configured with a flangedreceptacle 16 for receiving a modular secondary scrubber tower 18 thatpreferably rises vertically for providing a gravity fed scrubbingprocess. The scrubber tower 18 is shown providing a wet scrub process,however, it is also capable of supporting dry scrub processes andcombinations thereof. An exhaust module 20 is preferably provided abovethe scrubber tower 18 which substantially determines the rate of processflow through the system. The primary scrubber 12 is configured with apair of universal cooling sleeves 22, which provide modular receptaclescapable of receiving inlet modules whose process exhaust may be cooledtherein. The cooling sleeves 22 are attached to the primary scrubber 12with fasteners 24. A thermal reactor 26, having a process gas input port28, and a two stage scrubber inlet 34, having a process gas input port36, are connected to first and second cooling sleeves 22. The thermalreactor 26 contains a core through which the process gas, and preferablya heated source gas, are passed.

The rate at which process gas is drawn into the system through these twoinlet modules is substantially determined by the difference in pressurebetween the process gas source and the modular base unit 12. The exhaustmodule creates a negative pressure which aids in drawing the processgases through the system.

The system is shown having a pair of liquid scrubbers, specifically, aprimary scrubber 12 within the modular base unit, and a secondaryscrubber tower 18. Both liquid scrubbers are supplied with liquid fromthe reservoir 14 by a recirculation pump 38 that directs the liquidthrough pipes 40, (although tubing, passageways, and so forth, may beused) and a liquid flow sensor 42 to scrubber nozzles 44. The liquidspray 45 from the nozzles 44 within the primary scrubber directs theairborne chemical constituents into the reservoir 14 of liquid while theliquid from the nozzles 44 within the scrubber tower 18 directs theconstituents onto a wet scrubber grid 46. A sump pump 48 is fluidlyconnected to the modular base unit 12 and is capable of pumping outcontrolled amounts of liquid from the reservoir 14 through a facilitydrain 50 in response to an excessive fluid level within the reservoir ofthe base unit. A leakage sensor 52 is provided (preferably within acabinet or retention pan) for detecting the presence of liquid which hasescaped the system. The fluid level within the reservoir is registeredby fluid level sensors 54. A modular reagent addition system may beprovided to control pH and to enhance process chemical scrubbing withinthe present system. Fresh water, or alternatively fluids, may be addedto the system at any time, as represented by the fresh water inlet 55having a regulated input and capable of being monitored by anotherliquid flow sensor 42.

An assortment of sensors along with liquid and gas plumbing are showninterconnecting the elements of the system. Specifically, a line from anair source 56, and a line from an inert gas source 58 are shown. Variousaspects of the abatement process are monitored so that treatment mayproceed quickly and efficiently. Specifically, gas/air pressure sensors60 are capable of registering back pressure, such as occurs when athermal reactor becomes increasingly clogged. Flow sensors 62 providefor monitoring the flow of gas/air through the system. Temperaturesensors 64 allow the control system to monitor static temperatures andtrends in temperature which may be indicative of specific conditions.

The thermal reactor 26 is configured to facilitate quick replacement andcore changeovers, and is constructed with a top flange 66 attached uponan upper assembly 68 which is mounted to an elongated lower assembly 70whose lower end 72 is configured for attachment to the modular base 12(primary scrubber) by way of universal air cooling sleeve 22. The twostage inlet 34 is configured in a similar modular construction, with atop flange 74 attached to body assembly 76 whose lower end 78 isconfigured for attachment to the primary scrubber 12 through a universalair cooling sleeve 22. The top flanges of the thermal reactor 26 and thetwo-stage scrubber inlet 34 are configured with a universal port 80,that allows for the connection of an assortment of devices and sensors.

FIG. 2 shows a schematic for a thermal reactor 90 which utilizes athermal process to pyrolize and oxidize hazardous materials. Thechemical process mixture 92 flows into the reactor where it is directedby means of a nitrogen sleeve nozzle into a reaction chamber havinghousing walls 94. Preferably the reaction chamber comprises the internalvolume substantially of a cylindrical housing within which a reactioncore is retained. A preheated reagent gas 96 is introduced into thereactor through the porous wall 98 to mix with the process stream 92.The hot reagent gas causes reaction of these chemical species, therebycreating new chemical constituents including gas and particulate matter.The process stream constituents are shielded from the reactor wall bythe intruding hot reagent gas 96. Thus, these chemical constituents 102are swept through the reactor and mixed with a cooling gas prior toentering the subsequent scrubbing unit.

In FIG. 3A the thermal reactor 26 is shown assembled and in FIG. 3B thethermal reactor 26 is shown upon disengaging the flange 66 and removalof the core assembly 106 within which is retained a porous wall core108. Should the porous wall core 108 need replacement, the top flange 66can be easily disconnected, thereby, allowing all components whichcontact the process stream to be removed as an integral assembly. Oncethe porous wall core 108 is replaced, the new core assembly 106 islowered into the reactor housing and after the top flange 66 isreconnected, the reactor may be restarted. The complete maintenance canbe performed without disconnecting the individual chemical process linesand while the additional inlet modules continue substantially normaloperation. A reactor may be replaced with one having the same set ofreaction attributes, or one that provides a different set of attributes,so as to alter the reaction process used. It will further be appreciatedthat the reactor design, as shown in FIG. 3B, integrates a cleaningmechanism which can be used to clear the straight-through path of theprocess flow without the need of equipment shutdown. The cylindricalinterior of the porous wall core 108 can be cleared by the insertion ofa plunger having a cleaning head adapted to the inner diameter of theporous wall core.

FIG. 4, represents a falling film plasma reactor chamber between thewalls 132 of a housing, wherein the plasma reactor uses high voltagealternating current or pulsed direct current applied to spacedelectrodes 134 covered with a dielectric material 136 so as to createdielectric breakdown of the process gas within the large radial gap 138.Preferably, the opposing electrodes are implemented as concentriccylinders between which annular space is provided through which theprocess gas is passed. Use of conventional electrodes, covered withsolid dielectric, are susceptible to failure due to arcing when anyportion of the solid dielectric is compromised. The breakdown of thedielectric covering the electrode, and the associated arcing, ispreferably prevented within the present invention by utilizing a liquiddielectric 136 flowing over the electrodes to prevent dielectricbreakdown. The electrodes may, in addition, be coated with a fixeddielectric barrier over which the liquid dielectric 136 is directed. Theprocess gas mixture flows through the annulus created by the combinationof electrodes and dielectric materials and is sufficiently ionizedtherein to create general dielectric breakdown of the gas. A reagent gas141 is introduced into the process gas 140 within the plasma zone 138.The electrical energy deposited into the plasma dissociates atoms andmolecules of the gas stream which generates constituents comprisingenergetic electrons and reactive chemical species. Subsequent reactionof these chemical species with the reagents creates new chemicalconstituents including gas and particulate matter which in the course offlowing through the reactor contacts the liquid flowing over theelectrodes. Consequently, constituents of the chemical process streamare absorbed or reacted with the liquid and its constituents. Thus, theliquid simultaneously removes undesirable chemical constituents from theprocess stream and cools the process stream and reactor. The liquid iscollected in a plasma reactor fluid reservoir and pumped through afiltration system (separate from the fluid recirculation system of theprimary scrubber) to remove the undesirable chemical constituents andexcess heat prior to recirculating the liquid to the plasma reactor. Thetreated process stream 142 is swept through the reactor and mixed with acooling gas prior to entering the subsequent scrubbing unit.

The liquid reservoir, pump, and filtration system of the plasma reactorare modular and accessible to facilitate maintenance or replacement. Thecomplete maintenance described can be performed without disconnectingthe individual chemical process line and while the other reactorscontinue normal operations. With the basic scrubber inlet, the chemicalprocess flow is redirected by means of a nitrogen sleeve nozzle into theuniversal cooling air sleeve. Subsequently, the process stream is mixedwith the cooling gas prior to entering the following scrubbing unit. Theinlet design integrates a cleaning mechanism which can be used to clearthe straight-through path of the process flow without any equipmentshutdown.

Referring again to FIG. 1, it will be appreciated that the scrubbertower 18 can accommodate various distinct scrubbing modules. A firstscrubbing arrangement is shown in FIG. 1 as a single extended height,high efficiency counter-current secondary wet scrubber with a packed bedgrid 46 which interfaces with the liquid recirculation system to providelong residence times and high liquid-to-gas ratios. Numerous scrubbermodules may be arranged individually or in combination. As an example ofa second scrubbing arrangement (not shown), a pair of scrubber modulesare incorporated into the scrubber tower 18. By way of example, a lowerscrubber module provides an abbreviated height, moderate efficiencycounter-current, packed bed liquid scrubber which also interfaces withthe liquid recirculation system, while an upper scrubber module providesa fixed bed dry scrubber with in-situ regeneration capability. Theconfiguration of the dry scrubber should preferably extend the utilityof the dry scrubber by lowering the probability of particulate cloggingand by reducing the concentrations of process stream constituents to beremoved by the dry scrubber. The dry scrubber preferably comprisesmultiple fixed beds of support material coated with reagent. Integral toeach bed are means for heating, gas flow, and liquid spray. Uponsaturation of each bed, an alternate bed is selected to treat theprocess stream. The saturated bed is then recoated with reagent andheated to promote drying and reagent activation. The modularregeneration system includes a reagent reservoir (not shown) and reagentpump (not shown).

The components of the present invention are preferably housed in acabinet (not shown) that facilitates custom configuration and expansionof the modular point-of-use chemical treatment system. A simplefastening system using only two types of fastening components with boltsis used to assemble the tubular aluminum cabinet frame and providecomponent mounting fixtures. The fastening system permits expansion ofthe cabinet without modification or disassembly of the existingstructure. Feasibility of the expansion process results from the on-siteassembly of components which are manageable both in size and weight.

The modular abatement system of the present invention may be implementedin various ways to support numerous and varied chemical process streams.It will be appreciated that the inlet modules utilized within the systemmay be configured in a number of ways without departing from theteachings of the invention.

FIG. 5 shows a modular abatement system 150 according to anotherembodiment according to the present invention which comprises a modularpoint-of-use chemical treatment system having interchangeable inletmodules which are connected into a common modular base unit whichpreferably comprises a primary scrubber unit 12. The primary scrubber 12contains four process stream inlets into which are shown connected aporous wall thermal reactor 152, a two stage scrubber inlet 154, afalling film plasma reactor 156, along with an unused inlet 158 which iscapped and purged with nitrogen.

The inlet modules utilized may provide any of numerous chemicaltreatments for the process flow. These inlet modules may comprise anycombination of thermal reactors, plasma reactors, particle collectors,scrubbers, and so forth. The inlet modules are configured for modularattachment to a modular base unit which preferably contains a chemicalscrubbing unit which is configured for modular attachment of a secondaryscrubber, and interchangeable particulate collectors, the combinationoptimized for the treatment of specific chemical mixtures. Everycomponent of the system is designed and packaged to minimize the timeand effort required for installation and maintenance and to maximizelifetime and performance. Integrated controls and safety interlocks arepreferably utilized within the system to permit simultaneous operationof several different inlet modules. The entire system, includingcontrols and cabinets, are preferably configured to provide for rapidreconfiguration, or expansion, of the treatment system.

Several universal cooling air sleeves 160 in FIG. 5 have been receivedwithin inlet holes along the top surface of the primary scrubber 12,which is often called a liquid spray chamber. The universal air coolingsleeves 160 provide a coupling that is capable of receiving any inletmodule and cooling its associated process stream. The universal aircooling sleeve 160 of each inlet module is shown connected to a coolingair supply line 184 that connects to a supply 186 of pressurized coolingair.

Within the primary scrubber 12 are located several liquid spray nozzles44 for creating a liquid spray 45. The liquid spray chamber functions asthe primary (wet) scrubber 12, the recirculation reservoir, and the sumptank. By integrating these functions, the requirement for using liquidisolation traps (commonly P-traps) is eliminated and thereby the needfor frequent maintenance associated with their use. The cylindricalshape of the chamber eliminates corners responsible for flow stagnationand sedimentation. The chamber volume is small by design to vigorouslyagitate the recirculation liquid. This agitation suspends the scrubbedsolids within the scrubbing liquid to promote extraction by the sump.

The individual, pretreated process streams are introduced into theprimary scrubber through the inlet modules which are coupled to theuniversal cooling air sleeves 160. As the process streams traverse thespray chamber above reservoir 14, soluble and reactive vapors as well asparticulate are removed by the wet scrubbing process. The liquid spraynozzles 44 are configured to create a spray 45, as curtains throughwhich the individual and combined process streams must pass beforemixing within the liquid of the reservoir 14 and then entering thesecondary scrubber in the scrubbing tower 164. The liquid spray nozzles44 are supplied with liquid from the reservoir 14 recirculated by pump38 through a fluid supply line 192. The liquid spray 45 washes thechamber walls and cools the combined process streams prior to enteringthe secondary scrubber. This spray configuration ensures that theindividual process streams are relatively cool and prescrubbed prior tomixing with adjacent process streams. A variety of gaseous andparticulate chemicals become concentrated in the recirculated liquid ofthe reservoir 14. Upon mixing with the other pretreated process streams,the combined process stream is swept, by recirculation, into thesecondary scrubber within the scrubbing tower 164.

Integral liquid recirculation is provided with a recirculation pump 38that receives fluid through a fluid pickup 182 which is coupled to fluidcarrying pipes 40 (or tubing, hoses etc.). The recirculating liquid ispreferably passed through a heat exchanger 166 so that the temperatureof the liquid may be controlled, typically by sufficiently cooling theliquid. The recirculation system also contains a resource recoverymodule 168 a, with an additional resource recovery module 168 bcontained prior to the sump drain 50.

The recovery module 168 a in the recirculation system providesincremental recovery of various constituents for either reuse, ordisposal, as the liquid repeatedly cycles through the system. Anotherrecovery module 168 b is placed in line with the sump drain so as toprovide recovery when draining liquid from the primary scrubber 12.

Additionally, a reagent system 170 preferably dispenses reagents intothe scrubbing liquid to promote additional reaction chemistries andimprove the solubility of materials scrubbed from the process stream.The reagent system comprises a reagent reservoir, reagent pump, andsensor-based controls which enhance the scrubbers. Many of these reagentchemicals can be recovered prior to sumping the liquid to a facilitydrain. Recovery of the reagent, which is used to improve scrubberperformance, can significantly reduce the cost of operating the systemas well as minimize the risks associated with transporting and refillingthe reagent supply. Certain chemicals used in the production processesalso have intrinsic value. Compounds in the chemical categories ofGroups III, IV, and V metals and nonmetals can be valuable as areclaimed material. The use of several technologies utilizingelectrochemistry, reaction chemistry, and separation techniques enablethe module to selectively recover compounds for immediate reuse orreprocessing. By way of further example, scrubbing efficiency of processstreams containing acid gases can be greatly increased by adding areagent such as potassium hydroxide, which reacts with the acid gas toform a salt which is soluble and easily extracted by the sump. However,the recovery of this reagent can be accomplished using electrochemicaltechnology with subsequent reuse by the wet scrubber.

Control of the liquid in the reservoir 14 is provided with a sump pump48 that intakes fluid from the reservoir through an inlet 182 andtransfers it to a drain 50. Sensors monitor the liquid flow and liquidlevels to regulate the operation of the recirculation-sump functions. Amaintenance access port 162 is preferably provided on the primaryscrubber. The primary scrubber 12 is preferably configured with anoutlet flange to provide for the connection of additional primaryscrubber sections to increase the length of the primary scrubber and forreceiving additional inlet modules.

The scrubbing tower 164 can be configured for secondary scrubbing withone or more distinct scrubbing modules. One embodiment of secondaryscrubber comprises a single extended height, high efficiencycounter-current, packed bed liquid scrubbing tower which interfaces withthe liquid recirculation system to provide long residence times and highliquid-to-gas ratios. The scrubbing tower comprises several feet of highperformance packing material 172, one or more perforated plates 174 tosupport the packing, several spray nozzles 44 to distribute 45 liquidover the surface of the packing 172, a lower flange 16 to connect thetower to the primary scrubber 12, and a top plate 176 to manifold thespray nozzles and mount the scrubber exhaust module 178. Treated streamspass through the exhaust module 178 which can provide for additionaltreatment, such as removing particulates while the exhaust system can beutilized to control process gas flow rate.

The inlet modules 152, 154, and 156 in FIG. 5 can be modularly connectedinto the abatement system 150 in accord with the needs of the processstreams being treated. Each of the inlet modules is supplied with inertgas through gas lines 188 from a connection 190 to an inert gas supply.

The thermal reactor 152 inlet module receives process gas through aprocess gas intake port 194 within the inlet head 196 which is attachedon the body 198 of thermal reactor 152. A gas heater 200 provides forheating of the reagent gases as they enter the thermal reactor 152. Thereagent gases may be supplied from a gas reagent system 202 thatcontrols the delivery of various reagents 203. The output of the gasreagent system 202 is preferably manipulated by the control electronicsof the system.

The modular abatement system 150 has been developed to allow for safeand efficient gas processing. To enhance safety, a series of additionalsensors are preferably utilized comprising a leak sensor 204 whichsenses any liquid accumulation from system leaks, a smoke detector 206,and an exhaust gas flow sensor 208 to assure that the process gases arebeing processed. It will be appreciated that the present abatementsystem is preferably mounted within a cabinet to further insure safety,however, it may be freestanding.

The treated process streams exit the system through the exhaust module178. Preferably the exhaust module 178 provides additional particulateremoval, demisting, and dew point depression, while increasing exhaustdraw. The preferred embodiment utilizes an exhaust module 178 that issupplied with air through a connection 180 to a regulated air supply,and includes ports for pressure and temperature monitoring. Two distinctmethods of particle separation are exemplified within the embodiment.

Upon entering the first section of the exhaust module 178, the processstream encounters a series of liquid-washed impactor plates which areconfigured for the nominal collection of particles within a givenparticle size range. Residual particulate from previous treatmentoperations as well as mist created by the spray nozzles is impacted ontothe plates and removed. FIG. 6 shows a first particle collector assemblyattached to the top plate 176 of the scrubbing tower, and comprises amounting assembly 251 which retains a series of impactor plates 252designed to efficiently remove particle diameters ranging from submicronto low micron. An impactor plate 252 is shown in FIG. 7 having a seriesof flow apertures 254 and mounting holes 256. The surfaces of the platesused for particle collection are continuously washed with scrubbingliquid from apertures 258 within the tubing of the spray nozzle 44 tominimize the accumulation of solids.

A second collector 260 is shown in FIG. 8 which comprises an air poweredejector that accelerates particles at right angles to a collectionsurface effecting removal of micron diameter particles. An air inputline 262 receives air at a predetermined pressure at a proximal end 264,which exits the input line 262 at a distal end 266. Process gas isevacuated from the scrubber tower into the collection manifold 268 andoutput through an exhaust port 270, which may alternatively be plumbedto additional equipment or locations. As the high speed air travelsthrough the ejector 260, it creates a vacuum draw as a result of venturieffect so as to draw up gases from the top of the scrubber tower intothe collection manifold 268. The ejector, therefore, provides for bothparticulate reduction and enhanced exhaust draw on the modular abatementsystem. Regulating the flow rate of the incoming air into 264 canprovide for regulation of exhaust draw. Additionally, the ejector 260lowers the exhaust gas dew point temperature to minimize downstreamvapor condensation. Thus, the combined process stream exits the modularchemical abatement system as a relatively clean and dry mixture of gaseswhich presents no immediate hazards to the personnel or the productionfacility.

The modular abatement system 150 is shown in FIG. 9 being fitted withfour thermal reactors 152. A pair of universal cooling air sleeves 160are shown separated from the primary scrubber 12 to aid in understandingthe mounting relationships. However, it should be recognized that theuniversal cooling air sleeves 160, are generally to remain attached tothe scrubber 12 when receiving any of a number of inlet modules. FIG. 10is a side view of the abatement system 150 which shows the cylindricalreservoir 14 and the orientation of the various fluid communicationpipes orthogonal to the length of the primary scrubber unit 12 tofacilitate the attachment of a series of plumbing connections which maybe rapidly attached or disengaged.

An embodiment of the modular abatement system 150 is shown in FIG. 11having an alternative arrangement of two scrubbers 282, 284 that formthe scrubbing tower 164. The lower scrubber 280 is an abbreviatedheight, moderate efficiency counter-current, packed bed liquid scrubbingtower. This short scrubber provides the same features as the extendedheight tower yet has lower performance as a result of the smaller amountof packing material 284 used. The upper scrubbing module 282 comprises afixed bed dry scrubber with in-situ regeneration capability. The fixedbed dry scrubber comprises multiple chambers divided by walls 286 whichcontain high surface area solid packing material. Each chamber isprovided with a spray nozzle 288 for spraying liquid reagent onto thepacking material and a heater 290 for heating the packing material. Asthe combined process stream is continuously scrubbed, the capacity ofthe dry scrubber bed is reached and the combined process stream is thenredirected into an alternate dry scrubber bed while the initial dryscrubber bed is being regenerated. A regeneration system (not shown)comprising a reagent reservoir, a reagent pump, and sensor-based controlperiodically replaces the reagent coating on the surfaces of the solidpacking material. Upon recoating, the solid packing material is heatedto dry and activate the reagent coating.

One of the inlet modules for use with the modular abatement system isthe scrubber inlet module 154 of FIG. 12. This inlet module is mountedto the universal cooling air sleeve (not shown) by way of a flange 300that attaches to a cylindrical inlet chamber 302. This inlet 154 for theprimary scrubber 12 utilizes two mixing stages that eliminate backmixing of downstream gases, in particular those which were introducedinto the scrubbing unit from separate process inlets. The first mixingstage is accomplished by an inert gas sheath 304 which isolates theinlet nozzle 306 within the inlet head 308 from the second stage. Inertgas enters from an inert gas inlet 310 and mixes with the process streamwithin the increased diameter past the inlet throat 312 thereby reducinggas velocity. The second stage is accomplished by the inlet exhaustnozzle 314 extending into the universal cooling air sleeve (not shown).The inlet module 154 integrates a cleaning mechanism which can be usedto clear the straight-through path of the process stream without anyequipment shutdown. The inlet top plate 316 may be removed from theinlet head 308 to facilitate periodic inspection and cleaning and alsoprovides a universal access port for monitoring process stream pressure.Thus, the back pressures on all process lines are individually andsimultaneously monitored. The complete maintenance, as described, can beperformed without disconnecting the individual chemical process lines,and without disrupting the normal operations of the other inlet modules.A scrubber inlet housing 320 is depicted in FIG. 13 comprising anenclosure 322, a top cap 324, and an attachment clamp 326. The scrubberinlet housing 320 protects and insulates the scrubber inlet 300.

A porous wall thermal reactor 152 is shown in FIG. 14 which by way of athermal process pyrolizes and oxidizes hazardous materials passedthrough it from the process stream. The thermal reactor 152 comprises anprocess gas inlet port 194 within the inlet head 196 that is attached toa housing 198. The process gas is exhausted from an exhaust nozzle 328.The thermal reactor has a gas input connection 330 which is connected toa gas heater 200 for preheating the gas as it enters the thermal reactor152 so as to increase reaction levels. Modular fasteners 332 areprovided on the lower portion of the housing 198 for retaining a thermalreactor to the universal cooling air sleeve. These modular fasteners 332preferably comprise a quick-release mechanism that may be manuallyoperated so that replacement of the inlet module may be quicklyperformed. Annularly disposed within the inlet head 196 of the thermalreactor 152 is a sleeve nozzle 340 which is shown in FIG. 15. Wheninserted within the inlet head 196 of the thermal reactor as shown inFIG. 14, the top plate 342 (FIG. 15) forms the top of the inlet head.Referring again to FIG. 15, handles 344 are provided on the top plate342 so that an assembled thermal reactor may be manipulated forattachment or removal from the system. Standoffs 346 attached to the topplate 342 connect to a process gas receiving flange 348 that has acentral process gas passageway 350. When installed within the inlet head(196 of FIG. 14) the area of the standoffs 346 provides a process gasreceipt chamber 352 which is in fluid communication with a process gaspassageway 350. An inert gas receiving flange 354 is attached below theprocess gas flange with a passageway 356 which is annularly disposed onthe passageway 350. A chamber 358 receives inert gas from a coupling onthe inlet head and the inert gas is passed through passageway 356,annularly disposed about and separated from passageway 350, such thatthe process gas and the inert gas do not mix within the sleeve nozzle340. The nitrogen (or alternative inert gas) used for the sleeve flowmay also be premixed with reagent gas(es). A universal connector port360 in the top plate 352 of the sleeve nozzle 340 allows for theattachment of various equipment, such as injectors, and igniters. Forexample, an injector can be inserted through the universal connectorport 360 to premix reagent gas(es) into the process stream within theinlet nozzle or downstream within the reactor chamber. Alternatively, anigniter can be inserted through the universal connector port 360, orsimilar, port to initiate combustion reactions within the reactorchamber.

The housing 198 of the porous wall thermal reactor (PWTR) 152 is shownin FIG. 16 with a porous wall core 362. The exterior shell 364 of thehousing 198 is shown attached between an upper housing plate 366 and alower housing plate 368. The process gas exhaust tube 328 is shownattached within the lower housing plate in fluid communication with thecore 362. An intermediary wall 370, shown in a preferred insulatedconfiguration, is positioned between the porous wall core 362 and theexterior shell 364 of the thermal reactor 152. The interior area of thethermal reactor bounded by the intermediary wall 370 forms the reactionchamber for the thermal reactor, with the exterior of the intermediarywall providing insulation to reduce energy loss and reduce the risk ofburn injuries. The annular area disposed within the housing 198 butoutside of the reaction chamber may be filled with insulation layers,various forms of conventional high-temperature insulation may beutilized, such as fibrous insulation. The output of the heater 200 isdirected to the reaction chamber which is interior of the intermediarywall 370. A ceramic conduit 372 between the exterior shell 364 of thethermal reactor and the intermediary wall 370 directs the hot gases tothe reaction chamber. To simplify maintenance and cleaning, the porouswall core 362 of the thermal reactor is preferably configured having aninternal cylindrical volume, bounded by the porous wall tube.

The porous wall core 362 as shown in FIG. 17, is preferably constructedwith an inner tube 376 comprising a perforated alloy sheet rolled andwelded to the nominal dimensions. The second part of the tube,preferably the outer portion, comprises a fine mesh alloy screen 378which is rolled and attached, such as by welding, to the inner tube 376.It will be appreciated that the mesh may be alternately, oradditionally, attached to the inner surface of the inner tube, althoughthis is perhaps less preferable due to manufacturing considerations.FIG. 18 is an alternative embodiment of the porous wall core 380 that isconfigured for use within a cylindrical reaction chamber, to maintain asimilar spacing from tube to wall when using a cylindrical core in aconical housing. The tubes preferably contain a retention mechanism,such as exemplified within the embodiment with a locking pin 382proximal to the upper end of the tube. The inner tube 376 provides thephysical support structure for the outer tube 378 which ensures balancedhot reagent distribution into the reactor chamber. Thus, preheatedreagent gas is introduced through the porous reactor wall which mixeswith the process stream. The hot reagent gas causes reaction of thesechemical species, thereby creating new chemical constituents includinggas and particulate matter. The process stream constituents are shieldedfrom the reactor wall by the intruding hot reagent gas. This shieldingeffect requires that the pressure across the fine mesh alloy screenremain relatively constant as the chemical process mixture traverses thereactor chamber.

FIG. 19 is a top view of the porous wall thermal reactor housing 198with the inlet head removed wherein the relationship of the heater 200,exterior shell 364, inlet port 194 and process gas exhaust 328 may beseen. FIG. 20 shows the ceramic conduit 372 for mounting within the PWTRfor directing the heated gas to the interior of the reaction chamber.

The preferred embodiment of the porous wall tube provides high thermalconductivity, low thermal mass, low pressure drop, and oxidationresistance. One of the chief objectives of the modular system is tofacilitate reconfiguration and maintenance. To this end, thedesirability of low thermal mass should be appreciated. The core oftypical porous wall thermal reactors (PWTRs) utilizes thick ceramicmaterials contained within the reactor housing. These ceramic materialshave a large thermal mass and are therefore very slow to cool downsufficiently to allow for replacement. The present invention by contrastis designed using different materials and operating principles so that acore with low thermal mass and pressure drop may be utilized.

The operating principle of the PWTR of the present invention should beunderstood so as to appreciate how the present invention is capable ofutilizing a design with low thermal mass and low pressure drop. Aninherent requirement of this approach is maintaining a relatively equalpressure distribution across all of the orifices comprising the porousreactor tube. Four features of the reactor substantially maintain thiscritical pressure balance: (1) the hot reagent gas flow; (2) the meshsize utilized within the alloy screen; (3) the injection of the hotreagent at the top of the housing which is directed tangentially to theporous wall tube; (4) the complimentary geometric shapes of the porousreactor tube and the reactor housing elements. Three preferredgeometries of the porous reactor tube and reactor housing facilitatePWTR operation and are configured as either: (1) a cylindrical porousreactor tube within an inverted conical reactor housing; (2) a conicalporous reactor tube within a cylindrical reactor housing; or (3) aconical porous reactor tube with inverted conical reactor housing. Thereactor housing elements also contribute to the overall efficiency andease of reactor maintenance.

The heat recovery feature of the PWTR modules, coupled with their lowthermal mass heater, substantially reduces heat loss; while theinsulation eliminates a hot surface hazard which would otherwise existrelative to the outer reactor housing. The core is located near thecenter of the reactor contained within the inner walls of the reactorsection. To pass the gasses through the insulating outer area to thereactor chamber, an insulated conduit is preferably connected betweenthe exterior shell and the reaction chamber interior of the intermediarywall. The preferred embodiment of the thermal reactor reduces both thecost of fabrication and the energy requirement sufficiently to makeindividual treatment of process exhaust streams economically feasible.Furthermore, to enhance modularity while increasing efficiency, a numberof parameters of treatment may be individually controlled, such as, thereagent gas flows of individual reactors, the addition of reagent gases(added through the inert gas sleeve or an injection nozzle extendinginto the inlet nozzle), and the temperature of operation. In addition,the individual treatment of the process exhaust streams precludesproblems with mixing incompatible gases thereby preventing undesirableevents ranging from the formation of secondary hazardous by products toexplosive reaction of highly energetic molecules. Thus, processedchemical constituents are swept through the reactor and mixed with coolgas from the cooling air sleeve prior to entering the subsequentscrubbing unit.

Conventional reactor cores operate by different principles and utilizeceramics, metal-ceramic composites (either sintered or unsintered), orvarious other compositions; typically including a ceramic material.These ceramic porous walls often use a composite matrix having a binder.The thickness of the composite typically being in the range fromone-quarter inch to one-half inch. The internal porosity may account forup to 45% of the volume with average pore sizes of 37 microns or less indiameter.

The PWTR of the invention, however, utilizes a metal mesh for providingreagent gas distribution, not for facilitating combustion, radiantfunctions, or catalysis. The preferred embodiment of the PWTR porouswall tube requires the use of a metal mesh which is extremely resistantto high temperature oxidation and in which no catalytic activity isrequired. Preferably the mesh utilized has a 200×200 mesh screen,although the mesh can range from 25×25 to over 500×500 depending on wiresize, structure, and construction. The 200×200 mesh of the present PWTRprovides an open area of 34% with average opening size of 74 microns ormore in diameter. A comparison of pressure drop versus flow rate for aporous composite matrix and the PWTR tube further distinguishes the flowcharacteristics of the two approaches. For a flow rate of about 7 cubicfeet per minute (cfm), the pressure drop in the composite matrix exceeds8 inches of water column; while the pressure drop across the PWTR tubeis less than 0.1 inch of water column. The extremely low pressure dropacross the PWTR tube highlights the importance of the componentgeometries and reagent gas flow control. It will be appreciated,therefore, that the porous wall reactor tube, as a single layer alloymesh, creates a multitude of low pressure drop orifices rather than arelatively thick granular or fibrous matrix of ceramic or metal which iscompressed or fused together to create a multiplicity of relatively highpressure drop “tortuous paths” (i.e. permeable wall).

In addition, the low thermal mass and high thermal conductivity allowsfor rapid component cooldown, and a reduced “warm up period” duringstartup, while providing mechanical strength and dimensional stabilitywhich are critical for allowing rapid maintenance access and simplecomponent replacement. These concepts are fundamental to fully realizingthe benefits of component modularity.

To further support the system modularity, the porous wall thermalreactor (PWTR) 154 as shown in FIG. 21A contains an integral core 362attached to the inlet head 340 as a core assembly. The core assembly isdesigned to be removed as a single unit in a simple operation, as isshown in FIG. 21B wherein the core assembly 383 comprising the inlethead 340 and the porous wall core 362 have been removed. The integralcore design coupled with the other beneficial factors allow forinterchanging of cores to optimize the geometry of the reactor fordifferent hot reagent flow and process stream flow requirements.

When the reactor becomes less efficient, perhaps as detected by anincrease in the aforementioned back pressure, the reactor core should beeither cleaned or replaced. FIG. 22 depicts an additional cleaningfeature which facilitates reaction efficiency and low maintenanceoverhead. The sleeve nozzle 340 of the thermal reactor is shown with acleaning device 384 slidably inserted therein. The cleaning device 384comprises a rod 386 having a handle 388 attached to a proximal end, anda core cleaning element 390 attached to the distal end. When insertedwithin a PWTR the handle may be manipulated up and down SO that thecleaning element 390 is brought into contact with the interior of thecore to clear the straight-through process flow path without the need ofan equipment shutdown. Should the porous wall tube need replacement, thetop flange of the reactor can be easily disconnected, thereby allowingall components which contact the process stream to be removed as anintegral assembly. A replacement porous wall tube and its associatedgaskets may be simply connected to the inlet sleeve to form a coreassembly that is then lowered into the reactor housing. Uponreconnecting the top flange, the reactor may then be restarted.Typically, a reactor operating at 600° C. can be shut down for serviceaccess within 5 minutes and returned to normal operation within 10minutes. Complete maintenance, as described, can be performed withoutdisconnecting the individual chemical process line or halting anycontrolled functions of the reactor, and without disrupting the normaloperations of the other inlet modules being used within the system. Tofurther reduce the cost of operation, individual reactors can be placedin idle mode to conserve energy whenever upstream process equipment isoff-line for maintenance. Additionally, should all reactors be placed inidle mode, the fresh water flow is preferably reduced to a rate whichmerely compensates for evaporative water loss.

The universal cooling air sleeve 160 is shown in FIG. 23 and FIG. 24which provides a universal modular coupling for mounting any of avariety of inlet modules to the primary scrubber of the system. Theuniversal cooling air sleeve 160 comprises a base member 392, which ispreferably circular, into which a sleeve 394 has been attached, such asby pin 396. The length and type of sleeve may be preferably changed toalter the mixing characteristics of the process gas entering the primaryscrubber. The lower portion 398 of the base member 392 is configured forsealed attachment to an opening in an upper surface of the primaryscrubber to which it may be attached with fasteners which are insertedthrough recesses 400. When attached to the primary scrubber, the basemember 392 is capable of receiving an inlet module into throat 402,wherein a fastener attached to the inlet module 402 engages a matingfastener 404 attached or configured within the base member 392. Anannular ring 406 receives cooling air through an air inlet tube 408,such that the cooling air may be directed through a slot 409 between thebase member 392 and the annular ring 406 for cooling the process gas asit begins to enter the primary scrubber. It will be appreciated that theannular ring 406 may be configured in various ways to direct the flow ofthe cooling air for specific applications.

The cool air, or gas, is received through an air inlet tube 408 whichdirects the gas for tangential injection into the cylindrical housing ofthe base member 392 for distribution within the tubular sleeve 394. Aring-shaped aperture 406 is formed by the upper end of the tubularsleeve and the inside upper face of the cylindrical housing to ensureequal air flow. The tubular sleeve 394 can easily be replaced to varylength and thickness. Thus, the volume and velocity of the appliedcooling can be varied to address various process stream treatmentrequirements. Consider the example of the universal cooling sleeve 160into which is retained a thermal reactor. The inlet exhaust nozzle ofthe thermal reactor extends into the universal cooling air sleeve, suchthat cool air isolates the exhaust nozzle from the droplets and vapor ofthe scrubbing liquid. The process gas mixture, additional nitrogen, andclean, dry air are thereby swept from the thermal reactor into thesubsequent scrubbing unit.

The cooling air sleeves simultaneously dilute and cool the individualpretreated process streams as well as prevent the liquid mist and vaporwithin the spray chamber from contacting the exhaust nozzles of theinlet. Thus, the dilution minimizes the risk of undesirable chemicalreaction or physical accumulation, while cooling reduces liquid vaporformation and the consequent nucleation of liquid aerosol, and the airsleeve precludes the wetting of critical surfaces subject to corrosionor particulate accumulation.

In keeping with the ability to address a variety of treatment regimenswithin the modular system of the invention, the flow of air, or gas,through the universal cooling air sleeve is preferably regulated. Theregulation may be provided by an electronic valve that is manipulated bythe control electronics. However, for a large number of treatmentapplications the flow of cooling air may be preferably controlled byutilizing interchangeable flow orifices, which restrict air flow to apredetermined level. The amount of cooling air required for a particularapplication is determined largely by the reactor, or inlet type, and theprocess stream treatment requirement. Selecting nominal gas flows fortreating individual process streams reduces the demands placed uponsubsequent modules used to treat the combined process stream.

To facilitate control of the modular system various parameters of theinlet modules are monitored such that the controller may optimize theprocess, provide for safety alerts and shut-downs, and facilitate thescheduling and performance of maintenance. One such parameter that ismonitored within the exemplified embodiment is the pressure of theprocess stream within each thermal reactor. For example, the use ofpressure monitoring within the inlet heads of the thermal reactors toregister the process stream pressure. One benefit of monitoring thepressure is that the registration of back pressure provides a measure ofreactor core condition. The back pressures on all process lines aretherefore individually and simultaneously monitored.

In summary, the PWTR of the present invention provides numerous inherentadvantages including simplicity, low cost, robustness, adaptability, andserviceability, which result from the novel approach utilized.

The third inlet module shown in FIG. 5 is a falling film plasma reactor156 (FFPR). The electrical energy deposited into the plasma dissociatesatoms and molecules of the gas stream constituents generating energeticelectrons and reactive chemical species. Subsequent reaction of thesechemical species creates new chemical constituents including gas andparticulate matter which in the course of flowing through the reactorcontacts the liquid flowing over the electrodes. Consequently,constituents of the chemical process stream are absorbed or reacted withthe liquid and its constituents. For efficiency, the surface area forthe plasma reaction should be maximized. The FFPR of the presentinvention utilizes a series of concentric sleeved sections, preferablycylindrical, through which gases are passed. Furthermore, the FFPRutilizes a liquid dielectric which is made to flow as a film over theconductors, thus the term “falling film” so as to provide an efficientdielectric that is not prone to shorting. The process stream isintroduced into the FFPR 156 through the inlet 410 at the top insulatingendpiece 412 which together with a bottom insulating endpiece 414maintain the concentric and tubular geometry of the annular layers ofthe FFPR. The process stream is distributed and flows through theannulus formed between the exterior of an inner core 416 and theinterior of an outer cylindrical wall 418. The inner core 416 and outercylindrical wall 418 comprise nested tubular sections and passagewaysfor the distribution of liquids and gases. The exterior surface of theinner core 416 has been configured with metallic surfaces 420 which areconnected as a first electrode, while portions of the inner surface ofthe outer cylindrical wall 418 have been similarly configured as asecond electrode 422. A liquid dielectric 424 is then made to flow overboth the inner and outer electrodes 420, 422 to provide a dielectricbarrier over the electrodes as the process gas (shown by the arrows)passes between the electrode surfaces. The dielectric liquid isintroduced from a liquid cooling and distribution module 426 to a liquidinlet 428 at the bottom insulating endpiece 414 and distributed througha distribution stalk 430 within the inner core 416 to flow over the twoseparated sections of inner electrode 420, and similarly through achannel in the outer cylindrical wall 418 to flow over the secondelectrode 422. The dielectric liquid is distributed over the inner andouter dielectric barriers using weirs 432. The configuration of theinner dielectric distribution channel within the core 416 is morecomplex than that within the outer dielectric cylinder 418, as the core416 contains both and upper and lower weir and associated falling film.The plasma is created within the annulus 434 between the first electrode420 and the second electrode 422 by applying a high voltage sourcebetween the electrodes to create a plasma region therein. The processstream flows toward this plasma region and is in contact with thedielectric liquid 424. Prior to entering the plasma region, reagent gasis introduced into a reagent gas inlet 436 at the upper end of the FFPR156 and is directed through an outer transfer tube 438 and then exitsthrough a circular slot 440 where it enters the annulus 434 and mixeswith the process stream. The combined process stream is thereby treatedin the plasma region within the annulus 434 and exits the FFPR at theprocess outlet of the 442 of the bottom insulating endpiece 414. Thebulk of the dielectric liquid 424 is separated from the treated processstream and exits the FFPR at the liquid outlet 444 of the bottominsulating endpiece 446. The dielectric liquid 424 contacts the processstream during and after plasma treatment such that heat energy andreaction products may be captured and absorbed within the dielectricliquid 424. Therefore, the liquid is cooled and filtered prior torecirculating through the FFPR. Some of the dielectric liquid may beentrained by the treated process stream, therefore, a phase separator446 is connected to the process outlet of the FFPR 156 to collect andrecycle residual dielectric liquid 424. The treated process stream exitsthe phase separator at an exhaust 448 to enter the primary scrubberthrough a universal cooling air sleeve.

A falling film plasma reactor (FFPR) provides a number of benefits forthe treatment of process gases. The falling film plasma reactor useshigh voltage alternating current or pulsed direct current which isapplied to radially separated electrodes to thereby create a dielectricbreakdown of the process gas that is flowing within the large radial gapbetween the two electrodes. Typical plasma reactors often utilize fixeddielectric construction which can result in potential failure of thedevice by arcing between the electrodes as portions of the dielectricfails. These failures are prevented by using a dielectric liquid thatconstantly flows over the electrodes, or over a fixed dielectric barrierover the electrodes. A conductive liquid may also be utilized within theFFPR design such that the electrode itself is being constantly“renewed”. Appropriate dielectric liquids are preferably those having adielectric strength of approximately 30 kilovolts per millimeter, noflash point, low vapor pressure, a use temperature above 200 degreescentigrade, and high resistance to chemical reaction. Critical purposesof the dielectric liquid are: (1) to cool the electrodes and the soliddielectric barriers (if used); (2) to provide a dielectric barrier toarcing or enhance the dielectric barrier in combination with a soliddielectric material (if used); and (3) to distribute the electricalcharge more uniformly on and around the dielectric surfaces to precludecharge localization which otherwise can lead to catastrophic arcing. Anexample of an appropriate conductive liquid is a 10⁻⁴ molar solution ofcalcium carbonate in water. Materials can be added to the dielectric orconductive liquids to enhance their physical, electrical, and chemicalperformance for specific processing applications. High dielectricmaterials such as fine aluminum oxide particles can be added to increasethe dielectric strength of the liquid and increase the effectiveviscosity of the liquid. Ionic materials such as calcium carbonate canbe added to increase the electrical conductivity of the liquid andincrease chemical removal of gases such as chlorine and fluorine.

A preferred embodiment of the falling film plasma reactor for themodular abatement application is shown in FIG. 26 through FIG. 29. Thepreferred embodiment of FFPR 156 comprises four subassemblies: the innerelectrode assembly of FIG. 26, the outer electrode assembly of FIG. 27,the reactor housing assembly of FIG. 28, and the separator and mountingbracket of FIG. 29.

The inner electrode assembly 450 of FIG. 26 comprises an electrode withan associated lower dielectric barrier 452, distribution stalk 454, areactor top plate 456 having an electrical feedthrough 458 for receivingelectrical wiring and a reagent gas. An upper film support 462 and alower film support, on the exterior of the lower dielectric barrier 452,provide the electrode surfaces over which the dielectric film layer isto be disbursed. An outer transfer tube 464 retains the liquid in acolumn from the liquid inlet 466. The reagent enters the feedthrough 458in the reactor top plate 456 and is introduced into the top of the outertransfer tube 464 for combination with the process stream within thereactor annulus. The dielectric liquid fills the outer transfer tube 464up to and including the lower weir 468, and since the liquid is underpressure from the reagent gas it is driven through an inner transfertube 470 up into the upper weir 472. The distribution stalk 454initiates the liquid falling film in two places along the length of theinner electrode 450. The dielectric is distributed over the electrodesfrom outlet 474 at the upper surface of the upper weir 472 to provide afalling fluid film over the upper film support 462, while liquidsimilarly falls from outlet 476 at the upper surface of the lower weir468. A solid ring 478 is preferably located at the base of the innerelectrode assembly which upon removal cleans the inner surface of theouter electrode assembly.

The outer electrode assembly 480 of FIG. 27, comprises an outerelectrode 482 with associated dielectric barrier 484 and electricalfeedthrough 486, an outer insulating tube 488, a top insulating endpiece490 which initiates the liquid falling film in one place and introducesthe process stream, and a bottom insulating endpiece 494 which exhauststhe treated process stream and dielectric liquid while reintroducing thedielectric liquid for distribution to the inner and outer electrodeassemblies. The top insulating endpiece 490 provides a port 492 forprocess stream pressure monitoring. Thus, the back pressures on allprocess lines are individually and simultaneously monitored. A processgas inlet 496 receives the gas for treatment which is delivered througha process output 498. The liquid for the FFPR is input through the inlet500 and output after circulation through outlet 502. During treatmentthe dielectric liquid flows over the electrode from falling outlet 504.

A reactor housing assembly 510 as shown in FIG. 28, which provides EMIshielding and structural support. The reactor housing assembly 510comprises a top endcap 512, a bottom endcap 514, a top sleeve 516, and abottom sleeve 518 which are attached to the outer electrode assembly ofthe plasma reactor by fastening clamps 520, 522. To provide propershielding, the sleeves and endcaps are preferably fabricated from metal.

A phase separator 446 as shown in FIG. 29 separates entrained liquidsfrom the process gas being exhausted from the falling film plasmareactor. A pipe housing 524 is configured with an inlet chamber 526 withan inlet jet 528 for receiving treated process gas from the FFPR. Anexhaust nozzle 530 is fitted to the underside of the pipe housing 524. Aliquid outlet port 532 directs the liquid back for reuse in the FFPR. Athreaded-cap 534 seals the housing but can be removed for cleaning theseparator. Entrained liquid through the inlet jet impacts on the upperportion of the exhaust nozzle 530 for collection thereof, while theprocess gas passes from inlet to exhaust.

The FFPR comprises inner and outer electrode assemblies that may bequickly separated to simplify and speed maintenance procedures. Theinner electrode assembly may be lifted out of the outer electrodeassembly after disconnecting the top endcap and reactor top plate. Asthe inner electrode assembly is lifted out, the integral cleaningmechanism clears the annular flow path. The cleaning mechanism issimilar to the cleaning device described for the thermal reactors andcomprises a solid ring attached to the lower end of the inner electrodeassembly and having an outside diameter nearly equal to the insidediameter of the outer electrode assembly. When required, replacement ofreactor components or extensive cleaning is facilitated by easy accessto all reactor components. In general, the components of the FFPR areassembled using conventional threads, close tolerance fits, or O-ringseals. The liquid reservoir, pump, and filtration system are modular andaccessible to facilitate maintenance or replacement. The completemaintenance described can be performed without disconnecting theindividual chemical process line and while the other three reactorscontinue normal operations.

Several control subsystems are critical to the implementation of thediverse technologies integrated as interchangeable and modularcomponents, and to the optimization of the treatment technologiesassociated with each particular process stream. Three control subsystemsare utilized within the modular abatement system are pneumatic control,hydraulic control, and electrical control.

FIG. 30 shows a flow diagram which exemplifies the hydraulic controlsubsystem within the modular abatement system. The hydraulic controlsubsystem includes the fresh water supply 600, the liquid spray chamber610 (or primary wet scrubber), the recirculation loop 616, the sumpdrain 626, the wet scrubber reagent supply 602, the wet scrubber tower610, the dry scrubber reagent supply 604, the dry scrubber tower 612,and the particulate collector 614. Fresh water 600 is utilized as thebulk solvent in the liquid spray chamber 616, wet scrubber tower 610,and particulate collector 614. Water may also be used in the reagentformulation for the wet scrubber reagent or dry scrubber reagent. Ineach instance, fresh water is added using a shutoff valve andrestrictive flow orifice. The liquid spray chamber (or primary scrubber)functions as both a wet scrubber and the recirculation-sump tank 616.The integration of these functions permits elimination of a liquidP-trap which precludes a serious maintenance concern. All sources ofreagent and recirculation liquid drain into the liquid spray chamber.The recirculation loop 618 includes a heat exchanger 620 to cool therecirculation liquid prior to flowing into the primary spray nozzles(within the primary scrubber chamber), into the secondary spray nozzles(within the secondary scrubber tower), and into the particulatecollector 614 spray nozzles. Wet scrubber reagent 602 or fresh water 600is injected into the recirculation liquid prior to the secondary spraynozzles to maximize the efficiency and capacity of the wet scrubbertower.

FIG. 31 shows a flow diagram which exemplifies pneumatic flow within themodular abatement system. The pneumatic control subsystem includes inertgas purge 700, pressure sensors 702, auxiliary gas addition 704, andblower air supply 706. Inert gas purge 700 must be provided for theporous wall thermal reactors 708, plasma reactor 710, and the scrubberinlets 712. Therefore, individual purge lines include interchangeablerestrictive flow orifices to accommodate component and processrequirements, and shutoff valves to facilitate individual maintenance.Pressure sensors are used to monitor pressures on all process streaminlets, and to monitor air supply pressures to the porous wall thermalreactor 708 and the falling film plasma reactor 710. Monitoring processstream inlet pressure is important to allow diagnosing equipmentproblems and maintenance requirements. Auxiliary gases added to theporous wall thermal reactor and falling film plasma reactor promoteadditional reaction chemistries for treating the process streams.Enhanced reaction chemistries improve the efficiencies of the reactorsand improve both the efficiencies and capacities of the subsequent inletmodules used for treating the combined process stream. For example,adding a reducing agent such as hydrogen to a process stream containingfluorine promotes hydrogen fluoride formation which is readily removedby wet scrubbing and minimizes the formation of oxygen-fluorinecompounds which are difficult to remove by wet scrubbing. Individualauxiliary gas lines include interchangeable restrictive flow orifices toaccommodate reactor and process requirements, and shutoff valves tofacilitate individual maintenance. Air supply pressures are monitoredacross restrictive flow orifices which control air flow to the porouswall thermal reactors and falling film plasma reactors. Individual airlines include interchangeable restrictive flow orifices to accommodatereactor and process requirements, and shutoff valves to facilitateindividual maintenance. Air flow to the universal cooling air sleeves isalso controlled by interchangeable restrictive flow orifices 714. Thecooling air requirement is determined by the reactor or inlet type andthe process stream treatment requirement. Selecting nominal gas flowsfor treating individual process streams reduces the demands placed uponsubsequent inlet modules used to treat the combined process stream.

FIG. 32 shows a block diagram which exemplifies electrical circuits andcontrols within the modular abatement system of the present invention.The electrical control subsystem includes the main power circuit 800,the emergency power off circuit 802, the power distribution modules 804,the programmable logic controller (PLC) 806, the hardware safetyinterlock modules 808, and the reactor power supply modules 820. Themain power circuit 800 is designed to accommodate single and three phasepower at various voltage levels. The emergency power off circuit 802provides for immediate equipment shutdown and power isolation by anoperator or critical fault interlock. Power distribution modules 804 tapinto the main power circuit to breaker, interlock, and control powerinputs to components and modules. The power distribution modulesassociated with the plasma reactors 830, thermal reactors 814, dryscrubber 826, reagent supplies 824, and scrubber exhaust 828 areinterchangeable or removable to facilitate nominal equipmentconfiguration or reconfiguration. The programmable logic controller 806(PLC) utilizes a modular control program to recognize the installationof specific equipment modules and activate the requisite controlroutines. The sensors and switches 812 associated with specificsubsystem and module operation and control interface to the PLC 806 andto the hardware safety interlock modules 808. Critical safety functionsinterface directly between specific sensors and switches, specifichardware safety interlock modules, and the specific power distributionmodules. Reactor power control modules are required to provide specificpower and control functions for the porous wall thermal reactor and forthe falling film plasma reactor and associated components. Thus, theconfiguration, operation, safety, and performance integrity of themodular abatement system is ensured by the control subsystems.

It will be appreciated that the modular system of the present inventionlends itself for use in an automated manufacturing environment.Specifically, the control system of the present modular abatement systemmay be connected to a process control computer (not shown), or aback-end server for manufacturing processes, such that the operation ofthe system may be monitored and properly coordinated with the processesfor which process gas streams are being received. Furthermore, whenconfiguring the system to correspond with the processes, each inletmodule and other module or setting for use, can be provided withdesignator and called out by the process computer such that a technicianneed only pull out and attach the modules as called out to properlyassemble the correct system for the process stream.

Accordingly, it will be seen that this invention provides a method andexemplifies a number of system embodiments and aspects which provide forthe treatment of various process streams within the semiconductormanufacturing industry. It will be appreciated that the teachings of theinvention may be practiced in numerous alternative ways andimplementations without departing from the present invention.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the invention but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. Thus the scope of this invention should be determinedby the appended claims and their legal equivalents. Therefore, it willbe appreciated that the scope of the present invention fully encompassesother embodiments which may become obvious to those skilled in the art,and that the scope of the present invention is accordingly to be limitedby nothing other than the appended claims, in which reference to anelement in the singular is not intended to mean “one and only one”unless explicitly so stated, but rather “one or more.” All structural,chemical, and functional equivalents to the elements of theabove-described preferred embodiment that are known to those of ordinaryskill in the art are expressly incorporated herein by reference and areintended to be encompassed by the present claims. Moreover, it is notnecessary for a device or method to address each and every problemsought to be solved by the present invention, for it to be encompassedby the present claims. Furthermore, no element, component, or methodstep in the present disclosure is intended to be dedicated to the publicregardless of whether the element, component, or method step isexplicitly recited in the claims. No claim element herein is to beconstrued under the provisions of 35 U.S.C. 112, sixth paragraph, unlessthe element is expressly recited using the phrase “means for.”

What is claimed is:
 1. A falling film plasma reactor using high voltagealternating current or pulsed direct current applied to radially spacedcylindrical electrodes to generate dielectric breakdown of a process gaswithin a large radial gap comprising a first inner electrode having anouter surface, a second outer electrode having an inner surface, and aliquid dielectric, wherein said liquid dielectric is configured to flowas a film over said outer surface of said first inner electrode, andsaid liquid dielectric is configured to flow as a film over said innersurface of said second outer electrode.
 2. A falling film plasma reactoras recited in claim 1, wherein said dielectric liquid contacts saidprocess gas within said large radial gap.
 3. A falling film plasmareactor as recited in claim 2, wherein a reagent gas is introduced intosaid large radial gap.
 4. A falling film plasma reactor as recited inclaim 3, wherein said current causes a plasma which dissociates atomsand molecules of constituents of the said gas stream thereby causing achemical reaction and creation of reaction products.
 5. A falling filmplasma reactor as recited in claim 4, wherein at least one of saidreaction products is absorbed within said dielectric liquid.
 6. Afalling film plasma reactor as recited in claim 5, further comprisingmeans for mixing said process gas with a cooling gas, wherein saidprocess gas exiting said large radial gap is mixed with said coolinggas.
 7. A falling film plasma reactor comprising radially spacedcylindrical electrodes, a liquid dielectric configured to prevent arcingbetween the electrodes and a large radial gap between the electrodesconfigured to allow the liquid dielectric to flow over at least one ofsaid electrodes, and further configured to allow a process gas tocontact, said liquid dielectric flowing over at least one of saidelectrodes.